package com.blumov.fastbox.infrastructure.persistence.customtypes;

import java.io.Serializable;
import java.lang.reflect.Method;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.Properties;

import org.hibernate.Hibernate;
import org.hibernate.HibernateException;
import org.hibernate.type.NullableType;
import org.hibernate.type.TypeFactory;
import org.hibernate.usertype.ParameterizedType;
import org.hibernate.usertype.UserType;

/**
 * Implements a generic enum user type identified / represented by a single identifier / column.
 * <p>
 * <ul> 
 * <li>The enum type being represented by the certain user type must be set by using the 'enumClass'
 * property.</li>
 * <li>The identifier representing a enum value is retrieved by the identifierMethod. The name of
 * the identifier method can be specified by the 'identifierMethod' property and by default the
 * name() method is used.</li>
 * <li>The identifier type is automatically determined by the return-type of the identifierMethod.</li>
 * <li>The valueOfMethod is the name of the static factory method returning the enumeration object
 * being represented by the given indentifier. The valueOfMethod's name can be specified by setting
 * the 'valueOfMethod' property. The default valueOfMethod's name is 'valueOf'.</li>
 * </p>
 * <p>
 * Example of an enum type represented by an int value: <code>
 * public enum SimpleNumber {
 *   Unknown(-1), Zero(0), One(1), Two(2), Three(3);
 *   int value;
 *   protected SimpleNumber(int value) {
 *       this.value = value;
 *       }
 * 
 *   public int toInt() { return value; }
 *   public SimpleNumber fromInt(int value) {
 *         switch(value) {
 *          case 0: return Zero;
 *         case 1: return One;
 *         case 2: return Two;
 *         case 3: return Three;
 *         default:
 *                 return Unknown;
 *     }
 *   }
 * }
 * </code>
 * <p>
 * The Mapping would look like this: <code>
 *    <typedef name="SimpleNumber" class="GenericEnumUserType">
 *        <param name="enumClass">SimpleNumber</param>
 *        <param name="identifierMethod">toInt</param>
 *        <param name="valueOfMethod">fromInt</param>
 *    </typedef>
 *    <class ...>
 *      ...
 *     <property name="number" column="number" type="SimpleNumber"/>
 *    </class>
 * </code>
 * 
 * @author Martin Kersten
 * @since 05.05.2005
 */

public class GenericEnumUserType implements UserType, ParameterizedType {
	@SuppressWarnings("unchecked")
	private Class<? extends Enum> enumClass;
	private Class<?> identifierType;

	private Method identifierMethod;
	private Method valueOfMethod;

	private static final String DEFAULT_IDENTIFIER_METHOD_NAME = "name";
	private static final String DEFAULT_VALUE_OF_METHOD_NAME = "valueOf";

	private NullableType type;

	public void setParameterValues(Properties parameters) {
		String enumClassName = parameters.getProperty("enumClassName");
		try {
			enumClass = Class.forName(enumClassName).asSubclass(Enum.class);
		} catch (ClassNotFoundException exception) {
			throw new HibernateException("Enum class not found", exception);
		}

		String identifierMethodName = parameters.getProperty("identifierMethod", DEFAULT_IDENTIFIER_METHOD_NAME);

		try {
			identifierMethod = enumClass.getMethod(identifierMethodName, new Class[0]);
			identifierType = identifierMethod.getReturnType();
		} catch (Exception exception) {
			throw new HibernateException("Failed to optain identifier method", exception);
		}

		type = (NullableType) TypeFactory.basic(identifierType.getName());

		if (type == null) {
			throw new HibernateException("Unsupported identifier type " + identifierType.getName());
		}

		String valueOfMethodName = parameters.getProperty("valueOfMethod", DEFAULT_VALUE_OF_METHOD_NAME);

		try {
			valueOfMethod = enumClass.getMethod(valueOfMethodName, new Class[] {identifierType });
		} catch (Exception exception) {
			throw new HibernateException("Failed to optain valueOf method", exception);
		}
	}

	@SuppressWarnings("unchecked")
	public Class returnedClass() {
		return enumClass;
	}

	public Object nullSafeGet(ResultSet rs, String[] names, Object owner) throws HibernateException, SQLException {
		Object identifier = type.get(rs, names[0]);
		try {
			return valueOfMethod.invoke(enumClass, new Object[] {identifier});
		} catch (Exception exception) {
			throw new HibernateException("Exception while invoking valueOfMethod of enumeration class: ", exception);
		}
	}

	public void nullSafeSet(PreparedStatement st, Object value, int index) throws HibernateException, SQLException {
		try {
			Object identifier = value != null ? identifierMethod.invoke(value, new Object[0]) : null;
			st.setObject(index, identifier);
		} catch (Exception exception) {
			throw new HibernateException("Exception while invoking identifierMethod of enumeration class: ", exception);

		}
	}

	public int[] sqlTypes() {
		return new int[] {Hibernate.INTEGER.sqlType()};
	}

	public Object assemble(Serializable cached, Object owner) throws HibernateException {
		return cached;
	}

	public Object deepCopy(Object value) throws HibernateException {
		return value;
	}

	public Serializable disassemble(Object value) throws HibernateException {
		return (Serializable) value;
	}

	public boolean equals(Object x, Object y) throws HibernateException {
		return x == y;
	}

	public int hashCode(Object x) throws HibernateException {
		return x.hashCode();
	}

	public boolean isMutable() {
		return false;
	}

	public Object replace(Object original, Object target, Object owner) throws HibernateException {
		return original;
	}
}
